Sump Size

I am trying to figure out how big of a sump to use on the 150 gallon tank I am about to do. I guess what i am trying to find out is how many gallons i should strive for.

 

according to the guy on melevsreef.com it should be as big as you can.He has been building sumps for a while lot of info on his site.The more water volume you have the better, fluctuations in temp and parameters are slower.
Here is what he says on size...
How do I decide the size?

Look at the area within the stand, taking note of any obstructions that are part of the construction of the stand. Note the hinges as well, as they can become a problem. How will you insert the sump? Through the front opening, or perhaps the rear? You may be able to remove the “style” (the upright piece of wood) from the front using a square-head screwdriver, giving you full access to drop in the sump.

Once you determine the area of space available, figuring out the length of the sump is pretty easy. Keep in mind that you may need to set aside space for a reservoir of fresh water to replace water lost due to evaporation, or perhaps a future Calcium or Kalk reactor.

The width of the sump should be the space from the front of the stand to the back, less 1”. Leave yourself a little room to adjust the sump into position.

Height is varied, but typically 16” is plenty. If the sump is too tall, it is very difficult to access things such as pumps, heaters, probes, etc. It might make it impossible to insert a skimmer in a tall sump, as there is only so much room under a tank. 16” tall works nicely, usually providing at least 10” of space to manipulate things. If you plan to implement a refugium, you’ll need to leave room for a light as well.

 

The sump/fuge is a great idea. However, I am more of a believer of more surface area for gas exchange being more important than water volume. So take that into consideration when choosing the shape of your sump. My 20g long is much better choice than my old 15g tall. Lots of surface area. The volume of water doesn't come into play as much because, with the exception of the fuge portion, the water level isn't really going to come more than 60% to the top. You want room for drainage in case of power failure. Keeping a sump full is never wise IMO.

Also, you need to be able to remove the sump without taking apart the display tank. If it springs a leak, you don't want to take apart your DT to get your secondary tank.

 

I would never fill as sump to the brim I am just trying to figure i guess a good size to use and ratio of water in sump to main tank.

 

As big as you can afford and fit under the stand, or wherever you put it. There is no downside to the largest possible sump.

The melev's reef site will have all the information you need, go take a look.

 

That's cool man.....just throwing it out there.....

 

The refugium is where you need the biggest size. the sump should be sized so that if power fails the water back flow from the display tank into the sump won't overflow.

On my 240 gallon I have a 40 gallon fuge and a 40 gallon sump. The fuge is 3/4 full and the sump runs with 5" depth water.

 

I know just trying to keep many others from responding along the same lines instead of answering the question no offense meant

 

Your sump as a "guideline" should be at least 20% of your tank (30 gal), if you have overflows with it's subsequent return IF one or both are able to back syphon to your sump it is ideal that the total amount of water that will be back syphon to the sump will not be enough to overflow your sump as a percaution for a blackout or other kind of power failure to the aquarium system. (ussualy this requires a sump/fuge larger than 20% of the main tank.

The way is to calculate knowing where you have your overflow and return from the sump how much water would back syphon untill the water level is below such items and build the water structure of the sump to have as much tank space (even overflowing the different chambers) to achieve the "back syphon failsafe" also remember to calculate the area for the skimmer you plan to use.

 

The first calculation is how much drainage will accumulate at shut down or power loss. Subtract fuge volume and any components that displace water including what their running holding capacities are as they will flow back too. In sump skimmers require proper depth for operation so a simple stand may be in order. The baffles installed extending from the bottom of the tank regulate water flow and the number of them restrict or delay to pump pickup. If you can figure your relative capacities that should help set baffle height and running depths. If not set up correctly you can starve or cavitate the pump at start ups. Eventualy it will equal out in that case but not at all ideal. That being said your return chamber should be of ample size and able to meet pump demand untill the flow catches up across the sump. Also be aware of return siphon from dt to sump from from the pump up line at power down. It will drain the dt to whatever depth it is set to. If it is half way deep in the dt it will drain the dt to half full until it breaks the siphon. To stop this condition just measure from the top edge of of the tank and bottom edge of the spillway, and put a small 1/8 hole in the return pipe at that same measurement facing in and down if possible as this hole will squirt water until tank level rises to cover it on restarts. The more Total volume you can achieve in sump gives you the greatest level of variation for evaporation fluctuations and safety buffer. Unless an auto top off is installed. Example... I'm running a 20 long and with the new addition of a skimmer it decreased my total holding volume and overall running water margin down like an inch or what im figuring like almost 2 gallons and I'm too shallow now in my pump area. Whick means now I have less margin for evaporation and have to stay on top of the top offs untill I can upgrade sump size. I hope this helps a little.